The present invention relates to ignition coils for internal combustion engines.
More particularly, it relates to an ignition coil which has a housing composed of synthetic plastic material and accommodating at least one main core surrounded by a return flux coil.
Ignition coils of the above mentioned general type are known in the art. In the known ignition coil the main core formed as a rod core is provided with a primary winding and a secondary winding, a flame-shaped return flux core surrounds the rod core, and a trough-shaped housing is composed of synthetic plastic material.
The return flux core which, as the main core, is composed of coated, soft magnetic lamellas is provided with two projections which are arranged in the diametrically opposite corners and formed as mounting ears. Each of the projections has a recess formed as an opening for mounting the ignition coil. The ignition coil is mounted on the cylinder head cover of the internal combustion engine by mounting means extending through the recesses, in particular screws or threaded pins.
During mounting or dismounting of the ignition coil the mounting means with the lamellas, and particularly the connecting lamellas engage on the upper and lower sides and these lamellas can be released from the remaining core lamellas and damaged. This can lead in undesirable manner to an operational disruption of the ignition coil.
It is further known to bundle the lamellas by a hollow rivet inserted in the recesses. This solution however has disadvantages. In particular, when there is a danger of radial narrowing of the throughgoing opening of the hollow rivet during the riveting process, the ignition coil can no longer be mounted. As a result, the hollow rivet is not placed in the form-locking manner on the connecting lamellas and in view of the high deformation cracks can occur at the flange of the hollow rivet. Therefore, setting takes place at the mounting connection extending through the hollow rivet under the action of dynamic loads, and the holding of the ignition coil is disrupted. Finally, the insertion of the hollow rivet into the recesses must be performed in a separate working step and its results must be tested in series manufacture which leads to high manufacturing costs of the ignition coil.